The present invention relates to a cleanser concentrate containing ionic and nonionic surfactants, also known as "tensides."
The removal of residues of biological materials such as those blood serums, cell cultures and bacteria media (e.g., agar) creates special difficulties when one deals with dirty surfaces of glasses, plastic vessels, hose systems, and linings of containers and equipment for laboratory diagnosis analysis.
The increasing automation of laboratory diagnosis procedures makes the cleansing process, which becomes necessary after every determination, an essential component in the reliable functioning of analysis systems. Hence, one must establish particularly high requirements for the reliable operation of special cleansers.
One of the most difficult cleansing problems is that presented by dried-on, biological material, comprised of cross-linked, often partially denatured proteins with poor solubility in water. In the thermal or oxidative cross-linking of proteins, free mercapto groups are transformed into disulfide bridges while, at the same time, the intramolecular structure-determining bridge bonds, (i.e., those bonds between the amphoterically reacting free carbonic acid groups, those bonds between carbonic acid groups and the primary amino-group, and the hydrogen bridge bonds) are destroyed. These functional groups then form other intermolecular or intramolecular bonds. This ionic cross-linking is accompanied by stereo-chemical configuration changes whereby the hydrophobic molecule segments of the proteins accumulate in a micellar fashion. The result of these processes is cross-linked proteins which are not soluble in water.
The conversion of the residues of such biological materials into partly or totally soluble residues can be attained only by using reagents that reverse the above-described chemical and physical cross-linking processes.
Prior to this invention, it had been necessary to use relatively aggressive media to reverse the cross-linking process. Contaminated containers and equipment would be placed for a long time in heavily acidic oxidizing media, such as, chromosulfuric acid. Alternately, alkaline media which caused hydrolysis of the biological components, especially by saponification of fats and alkaline splitting of the proteins and phosphatids, could be used.
However, these aggressive media can only be used on surfaces which can themselves resist extreme pH's and oxidizing conditions. For less resistive surfaces, it is necessary to use enzymatic cleansers wherein the decomposition or reduction of the biological material is accomplished by proteases and lipases. The primary disadvantages of enzymatic cleansers are that they are slow-acting and that their action may be halted by the presence of certain surface-active substances with enzyme-blocking effect.
Increasingly sophisticated laboratory diagnosis procedures and equipment place definite limitations on the use of cleansing methods of the kind hereinabove described. These limitations are a function primarily of the chemical resistance of the materials used in sophisticated equipment. Complex apparatus normally cannot be treated safely with chromosulfuric acid.
Detailed investigations show that use of strongly alkaline cleansing solutions results in considerable retention and chemical adsorption of alkali metal ions on glass and plastic surfaces. These ions cannot be removed by clean rinsing or washing. Their presence seriously interferes with quantitative analytical determination of Na.sup.+, K.sup.+ and Ca.sup.+ ions, which frequently takes place into the micro- and even nanogram range. The determinations of phosphate can also be affected by the presence of such ions.
In addition, it has been shown that surfactants can be bound adsorptively and resorptively on plastic surfaces. The presence of bound surfactants may seriously affect the determination of alkali and alkaline-earth ions and may hinder enzymatic procedures as well.
The adsorption and chemical sorption of cleansing agent residues on the surfaces of treated materials is a phenomenon more serious than commonly assumed. (G. A. Somorjai, "Chemical Bonds on Surfaces", Angewandte Chemie [Applied Chemistry], 89, 1977, pages 94-102). In order to prevent uncertainty and considerable fluctuations in the measured values due to adsorbed residues, it is necessary to use novel concepts in fabricating special cleansers for laboratory diagnosis instruments and other aids.
Accordingly, a major object of this invention is to provide a new special cleanser which does not require the aggressive agents required heretofore. Another object of this invention is to provide a new special cleanser which does not require the presence of sodium, potassium, calcium and phosphate ions or enzymes. A third object of the present invention is to provide a cleanser that minimizes adsorption on solid surfaces, whereby properly administered rinsing or washing processes using deionized water will give cleansed materials which exert only an insignificant or unmeasurable influence on subsequent laboratory diagnosis determinations.
According to theoretical concepts, these objects can be achieved by the following precepts:
(a) One can break, cancel or neutralize the intermolecular and intramolecular bridge bonds formed during the cross-linking of proteins. Such bonds can be described with the aid of the following formula diagram: ##STR1##
Breaking these bonds may be accomplished by using a cleanser containing an amphoterically dissociating agent which is believed to react through the resalting process with at least one of the functional groups participating in the bridge bond or formation. This can be done when, for example, the hydrochloride or sulfate of a weaker dissociating organic base is resalted with the free amino groups of the proteins. Alternately, the salt of a stronger organic base and a weak acid may act upon the free carbonic acid groups of the proteins.
In both cases, resolubilization is most favored if the remaining weaker dissociating ion partner of the amphoterically dissociating component of the cleanser is so hydrophilic that the remaining bridge binding ion of the protein is likewise hydrophilized due to salt formulation. Such a process would take place according to the following scheme: ##STR2##
(b) The hydrophobic molecule parts of the biological material, which are accumulated in a micellar manner, must likewise be hydrophilized. This can be achieved by means of certain surfactants, or by means of certain organic solvents. For this function, one can use chemical-physical action principles such as described by W. Schafer, "Pre-treatment of Metallic Surfaces with Chemical Agents," [Mitteilungen des Verins deutscher Emailfachleute e.V. [Bulletin of the Association of German Enamel Experts, Inc.], Volume 9, 1961, pages 25-34.
(c) In view of the specific use of the cleansers, they must be fabricated in such a fashion that they are essentially free of sodium, potassium, calcium and phosphate ions. This requires special pretreatment for the surfactants which are to be used in the cleansers. This problem is solved by the present invention.